Interpretive Summary: As Conservation Reserve Program (CRP) contracts begin to expire in 1995, environmentally fragile areas may be brought back into crop production. Proper management systems will be needed to maintain these areas in a productive, environmentally sound condition. A project evaluating runoff, erosion, and soil quality characteristics of a former CRP site in southwestern Iowa was initiated during the summer of 1994. No-till and moldboard plow tillage systems were established on Clearfield and Nira soils, which were then seeded to corn or soybean. Runoff rates from simulated rainfall events were significantly greater on sites returned to crop production than from adjoining, undisturbed CRP areas. Substantial soil loss was measured for the moldboard plow treatments, but no significant differences in erosion rates were found between the undisturbed CRP and no-till management systems. Reduced erosion rates on the no-till treatments were attributed to residual grass cover produced during the CRP period which remained on the soil surface and to enhanced water infiltration. No-till management maintained levels of soil quality similar to those of CRP by maintaining soil structural integrity and reducing losses of soil organic matter, associated with cropping, to 10% as compared to 19% to 22% losses with moldboard plowing. A no-till management system that helps to preserve existing surface cover and soil organic matter seems to be a suitable management practice for reducing potential for erosion and degradation of soil quality of former CRP areas which are returned to row crop production.

Technical Abstract:
In this study no-till and moldboard plow tillage systems were established on a former Conservation Reserve Program site. Runoff rates from simulated rainfall events were significantly greater on sites returned to crop production than from adjoining, undisturbed CRP areas. Substantial soil loss was measured for the moldboard plow treatments, but no significant differences in erosion rates were found between the undisturbed CRP and no-till management systems. No-till management maintained levels of soil quality similar to those of CRP by preserving soil structural integrity and reducing losses of soil organic matter associated with cropping. The CRP was initiated to remove environmentally fragile areas from crop production. Approximately 14.8 million hectares (36.5 million acres) of cropland, primarily west of the Mississippi, were enrolled in this program. To participate in the CRP, producers were required to convert cropland to vegetative cover for a 10-year period. In addition to reducing soil erosion, the CRP has served to decrease crop production, improve soil and water quality, and create better habitat for wildlife. Gebhart et al. (1994) found that establishment of perennial grass cover under the CRP resulted in significant increases in soil organic carbon at five selected locations within the Great Plains.